The invention relates to an air intake system of a multicylinder internal combustion engine with the cylinders of one row each being connected by intake pipes to a resonance chamber associated with this row, and with at least one connecting pipe running between the resonance chambers, into which fresh air flows and which has at least one controllable blocking element.
The performance of an internal combustion engine is directly proportional to the product of its stroke volume and the mean pressure. If an increase in stroke volume that is unfavorable with regard to exhaust volume and fuel consumption is to be avoided, a deliberate increase in mean pressure is all that can increase performance. This also causes the torque of the internal combustion engine to increase, since it is a direct result of the above product.
An air intake system with two resonance chambers is known from German Patent Document DE-34 24 433 A1. These chambers are connected together by two blockable resonance tubes, into which the incoming fresh air flows. From the resonance chambers, individual intake pipes lead to the intake manifolds of the cylinder heads. Depending on the connecting cross section of the chambers, controlled by throttle flaps, the mean pressure and hence the torque can be increased over a wide rpm range.
An object of the invention is to improve an air intake system of the above-noted type in such fashion that the mean pressure is increased as much as possible over the entire rpm range of the internal combustion engine.
This object is achieved by providing an arrangement wherein at least one resonance pipe is associated with each cylinder, said pipes being arranged to extend from resonance chambers of one row of cylinders to a common chamber common to the resonance pipes and provided with a fresh air inlet, and wherein a controllable blocking element is located in at least one of the resonance pipes associated with one row of cylinders.
In an internal combustion engine, when a resonance pipe is associated with each cylinder, in addition to the two-chamber resonance system formed by the resonance chambers and the connecting pipe in an internal combustion engine, said resonance pipe extending from the resonance chamber of the respective row of cylinders to a chamber common to all the resonance pipes, said chamber having a fresh air inlet and at least one controllable blocking element disposed in one of the resonance pipes of a row of cylinders, this chamber acts together with the resonance pipes to ensure that each cylinder receives an increased volume of fresh air, causing the mean pressure to rise. By means of the controllable blocking element, the resonance system available at a given time is adapted to the current rpm range of the internal combustion engine, so that a uniform torque curve at a high level is ensured without perceptible interruptions.
In one advantageous design, several of the resonance pipes of a row of cylinders can have blocking elements, thus ensuring further-improved adaptation of the resonance system to the engine rpm.
In this connection, the resonance pipes can have diameters and/or lengths that differ from one another, as a result of which the requirement for comparatively long and thin pipes for a favorable torque curve in the lower rpm range and relatively short pipes with larger diameters in the upper rpm range is taken into account.
A further improvement in adaptation to the requirements of the various rpm ranges is possible with a second connecting pipe, provided with a controllable control element, between the resonance chambers, said pipe working as a resonance pipe, like the first.
In another advantageous embodiment, identical pipe lengths of opposite resonance pipes and a flow-favorable straight-line pattern is achieved when the chamber is located in a plane of symmetry running in the lengthwise direction of the internal combustion engine, with the resonance chambers being located at a distance from, and parallel to, said plane.
The resonance pipe lengths then required can be obtained by mounting a chamber on the side of the connecting pipe away from the internal combustion engine.
Optimum inflow conditions in the intake pipes can be obtained if the segments of the resonance pipes located in the resonance chambers are cylindrical and flush with the intake funnels of the intake pipes. As a result, there is no crankshaft angle at which there is a shortage of air upstream from an intake funnel, possibly due to another cylinder being on intake.
In an internal combustion engine which, in addition to the blockable intake valves supplied by the intake pipe(s), has permanently operated intake valves, an additional resonance pipe can be associated with each cylinder that runs directly from the chamber to this valve. This permits operation that reduces emissions, in a comparatively low power range of the internal combustion engine, while when the load or rpm increases, the blocking elements are closed in stages, with the blockable intake valves being closed.
All blocking elements can be designed as rotary flaps that can be moved by pneumatic actuators. These in turn are triggered by timing valves controlled by an electronic control device of the internal combustion engine. This control device controls the timing valves as a function of the engine rpm and/or load (e.g., throttle flap position).